This application is the national phase under 35 U.S.C. xc2xa7 371 of PCT International Application No. PCT/JP98/04449 which has an International filing date of Oct. 2, 1998, which designated the United States of America.
The present invention relates to a refrigerating apparatus provided with an injection circuit.
Conventionally, as a refrigerating apparatus of this type, there has been one shown in FIG. 8. This refrigerating apparatus has a main circuit 57 in which a compressor 51, a condenser 52, a supercooling heat exchanger 53, a main expansion valve 54, an evaporator 55 and an accumulator 56 are connected in series.
A branch pipe 60 that branches from the main circuit 57 between the condenser 52 and the supercooling heat exchanger 53 is connected to an inner pipe 53A of the supercooling heat exchanger 53.
This inner pipe 53A extends from the downstream side to the upstream side inside an outer pipe 61 and is connected to an injection pipe 62. The branch pipe 60 has a mechanical expansion valve 63, and the degree of opening of this mechanical expansion valve 63 is changed by a signal from a thermosensitive tube 65. attached to the injection pipe 62.
The injection pipe 62 is connected to an intermediate-pressure portion 51A of the compressor 51. The injection pipe 62 has a solenoid controlled valve 66. By opening and closing this solenoid controlled valve 66, the injection of a gas refrigerant to the compressor 51 is turned on and off.
This refrigerating apparatus is improved in refrigerating efficiency by supercooling the refrigerant that is directed from the condenser 52 toward the main expansion valve 54 by a supercooling circuit constructed of the supercooling heat exchanger 53, the branch pipe 60 and the mechanical expansion valve 63. The refrigerating efficiency is further improved by injecting the branching refrigerant, which has absorbed heat in the supercooling heat exchanger 53 and comes from the branch pipe 60, from the injection pipe 62 into the intermediate-pressure portion 51A of the compressor 51.
It is sometimes better for the improvement in efficiency to send the whole refrigerant to the evaporator 55 without making the main-stream refrigerant branch into the branch pipe 60. In this case, the solenoid controlled valve 66 is closed so as to operate neither the supercooling circuit nor the injection circuit. It is to be noted that the mechanical expansion valve 63 cannot completely be closed due to its mechanism.
However, according to the aforementioned conventional refrigerating apparatus, noises occur due to the opening and closing of the solenoid controlled valve 66 provided for turning on and off the injection circuit, and this leads to the particular problem that noises are caused by the chattering at the time of change in pressure.
Furthermore, the provision of the solenoid controlled valve 66 only for turning on and off the injection circuit disadvantageously causes cost increase.
Next, FIG. 10 shows the refrigerant circuit of another conventional refrigerating apparatus. This refrigerant circuit is provided with a main refrigerant circuit 210 in which a compressor 201, a four-way control valve 202, an outdoor heat exchanger 203, a first expansion valve 205, a gas-liquid separator 206, a second expansion valve 207 and an indoor heat exchanger 208 are connected in series. This refrigerant circuit is further provided with a bypass circuit 211 for connecting the ceiling of the gas-liquid separator 206 to an intermediate-pressure portion 201a of the compressor 201. This bypass circuit 211 has a solenoid controlled valve 212. In this prior art example, the four-way control valve 202 makes a communication path indicated by the dashed lines during heating to execute a heating operation using the indoor heat exchanger 208 as a condenser. If the solenoid controlled valve 212 is opened during this heating, then a gas refrigerant from the gas-liquid separator 206 is made to pass through the bypass circuit 211 and injected into the intermediate-pressure portion 201a of the compressor 201. As described above, it is sometimes the case where the amount of refrigerant flowing through the indoor heat exchanger 208 that is operating as a condenser is increased by bypassing the first expansion valve 205 and the outdoor heat exchanger 203 and returning the gas refrigerant from the bypass circuit 211 to the compressor 201, for the improvement in efficiency.
FIG. 9 shows the above heating operation expressed by Mollier chart. As expressed by this Mollier chart, a flow rate Gc in the indoor heat exchanger 208 that serves as a condenser is the sum (Ge+Gi) of a flow rate Ge in the outdoor heat exchanger 203 that serves as an evaporator and a flow rate Gi through the bypass circuit 211. If the whole gas is injected from the gas-liquid separator 206 into the compressor 201, then the flow rate Gi of gas injection becomes (Gcxc3x97X). In this case, X represents the dryness (0.2 to 0.3, for example) of the refrigerant at the exit of the expansion valve 207. Therefore, the flow rate Gc in the indoor heat exchanger 208 becomes Gc=Ge/(1xe2x88x92X).
If frost is formed on the outdoor heat exchanger 203 in this heating operation, then a reverse-cycle defrosting operation is executed. That is, the four-way control valve 202 is switched over to make the communication path indicated by the solid lines, by which the outdoor heat exchanger 203 is operated as a condenser to melt the frost. Then, by opening the solenoid controlled valve 212 also in this reverse-cycle defrosting operation, it is enabled to return the gas refrigerant from the bypass circuit 211 to the compressor 201, increase the amount of refrigerant that is circulating from the compressor 201 to the outdoor heat exchanger 203 and rapidly melt the frost on the outdoor heat exchanger 203.
However, during this reverse-cycle defrosting operation, as shown in FIG. 11, the dryness at the exit of the expansion valve 205 is small (for example, X=0.1 or smaller), when the gas component of the refrigerant is little. For this reason, the circulating refrigerant has increased less in amount even if the gas injection is executed during the defrosting operation, and this has resulted in little effect on reducing the defrosting time.
Accordingly, the first object of the present invention is to provide a low-noise low-cost refrigerating apparatus capable of controlling the supercooling circuit and the injection circuit. The second object of the present invention is to provide a refrigerating apparatus capable of reducing the defrosting time.
In order to achieve the above objects, the present invention provides a refrigerating apparatus that includes a compressor, a condenser, a main expansion mechanism, an evaporator and a supercooling circuit having a supercooling heat exchanger provided between the condenser and the main expansion mechanism and includes an injection circuit for injecting a gas refrigerant from the supercooling heat exchanger into an intermediate-pressure portion of the compressor, the apparatus comprising:
a motorized expansion valve provided in a supercooling pipe that diverges from a main flow on the upstream side of the supercooling heat exchanger and reaches the supercooling heat exchanger.
In this refrigerating apparatus, the injecting operation of the injection circuit can be turned off by completely closing the motorized expansion valve. The degree of supercooling of the supercooling circuit and the amount of injection of the injection circuit can be set to the desired values by controlling the degree of opening of the motorized expansion valve to the desired degree of opening.
That is, according to this refrigerating apparatus, the motorized expansion valve plays the role of the prior art solenoid controlled valve and the role of the prior art mechanical expansion valve. This can obviate the need for the solenoid controlled valve, enabling the elimination of noises occurring in opening and closing the solenoid controlled valve or, in particular, the chattering noises. Furthermore, cost reduction can be achieved since the solenoid controlled valve is not needed. Therefore, according to this invention, the supercooling circuit and the injection circuit can be linearly controlled with reduced noises at low cost.
An embodiment comprises a first opening control section for setting the motorized expansion valve to a small degree of opening close to a completely closed state when the injection circuit is substantially stopping its operation.
In the refrigerating apparatus of this embodiment, by slightly opening the injection use motorized expansion valve even when the injecting operation is not executed, the possible generation of a clearance volume (dead space) can be prevented to enable the prevention of the reduction in volumetric efficiency of the compressor.
Another embodiment comprises a rectifier circuit for flowing the refrigerant sequentially into the condenser, the supercooling heat exchanger and the main expansion mechanism both in a cooling operation and a heating operation.
In this refrigerating apparatus, the refrigerant can be made to flow sequentially into the condenser, the supercooling heat exchanger and the main expansion mechanism by the rectifier circuit both in the cooling operation and the heating operation. Therefore, the supercooling and the gas refrigerant injection can be executed in both the cooling operation and the heating operation, enabling an improvement in efficiency.
An embodiment comprises a second opening control section for controlling the degree of opening of the motorized expansion valve to increase or decrease the degree of opening according to a refrigerant temperature of the injection circuit.
In this refrigerating apparatus, the injection flow rate is increased by increasing the degree of opening of the injection use motorized expansion valve when the injection flow rate is small, and the injection flow rate is reduced by decreasing the degree of opening of the injection use motorized expansion valve when the injection flow rate is great, by which the injection flow rate can be invariably maintained at the desired value.
One aspect of the present invention provides a refrigerating apparatus that includes a compressor, a four-way control valve, an outdoor heat exchanger, a main expansion mechanism and an indoor heat exchanger and executes a reverse-cycle defrosting operation, the apparatus comprising:
a liquid injection circuit for injecting a liquid refrigerant from the outdoor heat exchanger into the compressor during the reverse-cycle defrosting by bypassing the main expansion mechanism and the indoor heat exchanger.
In this refrigerating apparatus, the liquid refrigerant is injected into the compressor during defrosting by the liquid injection circuit. Accordingly, the amount of circulation of the compressor can be still more increased than in the case of gas injection. Therefore, the frost can be melted in a short time, allowing the defrosting time to be reduced.
Another aspect of the present invention provides a refrigerating apparatus that includes a compressor, a condenser, a main expansion mechanism, an evaporator and a supercooling circuit provided between the condenser and the main expansion mechanism and includes an injection circuit for injecting a gas refrigerant from the supercooling circuit into an intermediate-pressure portion of the compressor, the apparatus comprising:
a motorized expansion valve provided in a supercooling pipe that diverges from a main flow on the upstream side of the supercooling circuit and reaches the supercooling circuit.
In this refrigerating apparatus, the injecting operation of the injection circuit can be turned off by completely closing the motorized expansion valve. The degree of supercooling of the supercooling circuit and the amount of injection of the injection circuit can be set to the desired values by controlling the degree of opening of the motorized expansion valve to the desired degree of opening. That is, according to this refrigerating apparatus, the motorized expansion valve plays the role of the prior art solenoid controlled valve and the role of the prior art mechanical expansion valve. This can obviate the need for the solenoid controlled valve, enabling the elimination of noises occurring in opening and closing the solenoid controlled valve or, in particular, the chattering noises. Furthermore, cost reduction can be achieved since the solenoid controlled valve is not needed. Therefore, according to this invention, the supercooling circuit and the injection circuit can be linearly controlled with reduced noises at low cost.
One embodiment comprises a control means for turning on an injecting operation of the injection circuit by opening the motorized expansion valve when the compressor comes to have an operating frequency being not lower than a specified operating frequency.
In this refrigerating apparatus, the injecting operation is turned on when the operating frequency of the compressor is set to the frequency being not lower than the specified operating frequency. Therefore, efficient injection can be achieved with the amount of circulating refrigerant increased to a specified amount or more.